The present invention relates to the field of metallurgy, and in particular, to foundry practice wherein a device for heating, mixing and/or transferring metals in a liquid state applies certain effects of electromagnetism.
It is known in metallurgical practice that to obtain a semi-finished product, the metal must pass through a melting phase which is intended to place the metal in a suitable state for subsequent treatment including mixing of the metal with purification elements, refining, alloying or shaping the metal by transfer and solidification in different types of molds. In short, there are many operations that require heating, mixing and transferring means to place metals in a liquid form.
It is true that those skilled in the art who have been faced with these problems for many decades have found numerous solutions by resorting, among other things, to electromagnetic means.
Thus, French Pat. No. 1,600,320 discloses a furnace containing a metal wherein the bottom portion of the furnace includes three channels. Two of the channels are surrounded by closed magnetic circuits and coils which induce a current to heat and mix the metal. The third channel which is provided with an extraction pipe, is equipped at the point of intersection with the other two channels with an electromagnet having a field that acts on the induced current to create the force necessary to move the metal toward the interior of the furnace.
Such a device, however, has the following disadvantages. The device requires two different magnetic systems--one formed by the circuits and coils which generate heat and perform the mixing, and the other magnetic system formed by the electromagnet that assures the transfer of the metal. This arrangement requires the mounting of two separate electric feed lines with their associated measuring and control devices.
Moreover, the electromagnet is a source of considerable energy loss, both in the copper by the Joule effect, and in the iron by hysteresis and Foucault currents; in part, because it is fed with an alternating current. The induced currents which pass through the metal interact with the magnetic leaks of the circuits to produce an intense mixing of the liquid, hence disturbances occur at the level of the vehicled outputs and in the materials forming the channels. The energy dissipated by these leaks when added to the energy required to perform the normal functions of heating, mixing and transferring operations produces a relatively high consumption of electricity.
That device, while allowing for separate control of the heating and transferring operations, is nevertheless complex and a high energy consumer.